Polyolefin waxes are important for many application areas. Their use as additives in printing inks and surface coatings is attracting increasing interest. In printing inks, waxes increase the wear, abrasion and scratch resistance of printed products. In surface coatings, waxes serve not only to improve the mechanical properties of the coating surface but also to achieve matting effects (cf. Ullmann's Encyclopedia of Industrial Chemistry, Weinheim, Basel, Cambridge, New York, 5.ed., Vol. A 28, p. 103 ff). For the printing ink and surface coatings applications, the waxes are used in the form of solvent dispersions or pastes or else in solid micronized form. Micronization is carried out either by milling in suitable mills or by spraying from the melt, in each case with subsequent classification if necessary. The required average particle sizes are generally below 10 .mu.m.
For these applications, use has hitherto been made of waxes from various preparation processes. A customary method is, apart from free-radical polymerization at high pressures and temperatures, the preparation of waxes in solution using Ziegler-Natta catalysts comprising a titanium compound as catalytically active species (cf. DE-A-1 520 914, U.S. Pat. No. 3,951,935, U.S. Pat. No. 4,039,560, EP-A-584 586).
The nonuniformity of the products can be seen from a broad distribution of the chain lengths, i.e. the polydispersity, from the nonuniformity of the incorporation of comonomers within a chain and the distribution of the comonomer content between various types of chains. This leads to products having reduced hardness and containing volatile or extractable components.